a. FIELD OF THE INVENTION
This invention relates to a thermoplastic resin firm or sheet for chelate color printing and to a process for producing such a film or sheet.
B. DESCRIPTION OF THE PRIOR ART
A method has previously been known which involves forming on the surface of natural pulp paper a chelate color-forming layer composed mainly of a metal compound capable of forming a chelate compound on reaction with an organic compound, and printing this paper using a color forming ink composed of an aqueous solution containing, as a main constituent, an organic compound capable of reacting with the above metal compound, whereby color printing is effected by the formation of a chelate compound. This method, however, has the defect that where natural pulp paper is used as a substrate, the color forming layer intrudes deep into the spaces amoung the individual fibers of the substrate, and because the color forming ink is an aqueous solution, the resulting printed image becomes blurred or vague. Attempts have been made to remove such a defect ascribable to the use of natural pulp paper as a substrate by using a thermoplastic resin film or sheet as a substrate. However, since the surface of the thermoplastic resin film or sheet is smooth and is devoid of the ability to absorb color-forming ink, the sticking and drying properties of the printed image are insufficient and good printing is not obtained.